Process for heavy oil upgrading in a double-wall reactor

ABSTRACT

A process for reducing coke formation during hydrocarbon upgrading reactions using a double-wall reactor comprising the steps of feeding a heated feed water to a shell-side volume of the double-wall reactor to produce a heat transfer stream, the double-wall reactor comprising an exterior wall and an interior wall, a reaction section volume, a heating element configured to heat the heat transfer stream, wherein heat is transferred from the heat transfer stream to the reaction section volume, feeding the hot water return exiting the shell-side volume through a filter; mixing the filtered water stream with a heated hydrocarbon feedstock; feeding the mixed stream to the reaction section volume in a configuration counter-current to the heat transfer stream; reacting the reaction flow stream at a reaction temperature, wherein the heat transferred to the reaction section volume is operable to maintain the reaction temperature above the critical temperature of water.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority from U.S.Non-Provisional application Ser. No. 14/554,209 filed on Nov. 26, 2014.For purposes of United States patent practice, this applicationincorporates the contents of the Non-provisional Application byreference in its entirety.

TECHNICAL FIELD

This invention relates to a method and apparatus for reducing cokeformation during upgrading of heavy oil. More specifically, the presentinvention relates to a method and apparatus for upgrading heavy oil in adouble-wall reactor using supercritical water to reduce the formation ofcoke.

BACKGROUND

Increasing demand for gasoline and diesel requires more petroleumproducts of light and middle range distillates which can be mixed intogasoline and diesel pools. However, currently available hydrocarbonresources, most commonly include crude oil and other heavy fractions andheavy fraction distillates, requiring refining processes to generatedesired products.

Conventional refining processes upgrade heavy oil into light and middledistillate range products with the aid of thermal energy, catalysts, andhydrogen. Representative conventional processes include catalytichydroprocesses and coking processes. Catalytic hydroprocessing, such ashydrocracking, produces clean gasoline and diesel products, whereimpurities, such as sulfur, are minimized, but the premium quality ofthe products requires a huge consumption of hydrogen to produce. Cokingprocesses, where catalysts and hydrogen are not employed, utilizethermal cracking reactions to upgrade heavy oil into gases, lightdistillates, and middle distillates, but also produce large amounts oflow economic byproducts, such as solid coke.

A third option to upgrade heavy oil is the use of supercritical water. Alow dielectric constant makes supercritical water a good solvent fororganic compounds. Supercritical water has been used as a reactionmedium for certain chemical reactions such as oxidation and forupgrading hydrocarbons. Supercritical water is a good reaction mediumfor upgrading because hydrogen can be transferred from the water to thehydrocarbons. Thus, a huge supply of hydrogen gas is not necessary.Supercritical water acts as a diluent, diluting the hydrocarbons. Inupgrading heavy oil using supercritical water, as in thermal cracking, aradical is generated due to chemical bonds breaking. Molecularrearrangement follows radical propagation, including cracking,dimerization, and oligomerization. However, unlike in thermal crackingalone, upgrading reactions in supercritical water reduce the chance forradicals to be oligomerized, because the supercritical water acts as a“cage” to restrict the radicals. Radical species are stabilized bysupercritical water through the cage effect (i.e., a condition wherebyone or more water molecules surrounds the radical species, which thenprevents the radical species from interacting). Stabilization of radicalspecies is believed to help to prevent inter-radical condensation andthus, reduce the overall coke production in the current invention. Forexample, coke production can be the result of the inter-radicalcondensation.

Coke, or petroleum coke, is a solid material formed in upgradingreactions. The solid material may leave the reactor with the liquidproducts, but commonly remains as a layer on the inner surfaces of thereactor and process piping. To be useful, coke requires furtherprocessing and is therefore considered a less valuable by-product toupgraded hydrocarbons.

Coking is a significant problem in upgrading reactions. Coking increasesat increased temperatures. While the extent to which coking will occuris hard to predict, it is known that temperatures above 400° C. areenough to form coke. One reason coking is accelerated at highertemperatures is because radical formation is accelerated at highertemperatures. More radicals results in more oligomerization reactions,which increases the molecular condensation reactions or coke formation.

Hot spots contribute to coking in upgrading reactors. Hot spots occurdue to localized heating of a metal surface, such as a reactor wall. Ingeneral, localized heating is caused by an irregular or non-uniformdistribution of a direct heat source, such as a flame, an electricheater, a formation of an insulator on a metal surface, or an irregularfluid distribution on a metal surface. An example of an irregular fluiddistribution on a metal surface would be the stoppage of process fluidflow in a tubular reactor. Thus, a furnace or heater must be designedfor uniform distribution of temperature through the reactor walls. Onedesign feature is to coat the surfaces of reactors with heat transfermaterials to provide better heat distribution, but such heat transfermaterials often have short life spans and are expensive to replace. Asecond design option is to ensure a high superficial velocity of theprocess fluid through the reactor. A high superficial velocity canimprove temperature distribution. However, in some cases designing forhigh superficial velocity requires a high length to diameter ratio ofthe reactor tube which increases the cost of the reactor due to thematerial weight of the reactor tube. Any design should feature sensitiveinstrumentation for temperature monitoring throughout the reactor toprevent formation of hot spots. However, even with precise design andinstrumentation, hot spots in a direct heating system are inevitable. Atbest, a reactor design can hope to minimize the number and intensity ofhot spots.

Hot spots contribute to coking because they cause localized excessiveheating of the fluid in the reactor. The excessive heating causeslocalized coke formation on the inner wall of the reactor. Once the cokeforms on the inner wall both the size and intensity of the hot spot canincrease leading to more coke formation. Additionally, the cokeformation hinders accurate measurement of temperature in the reactor.

Coke formation during upgrading processes limits the functionality ofthe upgrading process. A reduction in the coke formed during upgradingwould lead to an increased yield of liquid hydrocarbon products. Cokeformation limits the run length, or residence time, the petroleum canspend in the reactor. Shorter residence times results in less efficientupgrading. Coke plugs the process lines causing an increase in thepressure of the process lines and the reactor. If the pressure increasesabove a certain point, the entire process must be shut down so the cokecan be removed. Otherwise the pressure build-up could cause mechanicalfailure of the plant equipment. Coke formation is one of the commoncauses for unscheduled shut-downs of refining processes.

Supercritical water reduces coke formation compared to a purely thermalprocess. The extent of coking prevention by supercritical water,however, depends on the type of heavy oil. Even supercritical water islimited in preventing coke formation because molecules, especially,heavy molecules, are not easily dissolved in supercritical water due totheir low solubility, so the larger molecules, such as asphaltenes, canbe easily converted to coke through radical mediated reactions.Additionally, supercritical water at higher temperatures has lowerdensity than heavy oil and that density changes more quickly as thetemperature rises at supercritical pressures. At 25 MPa, the density ofwater at 400° C. is 166.54 kg/m³ while at 450° C. the density is 108.98kg/m³. The relative difference in the density of heavy oil andsupercritical water causes settling of heavy molecules on the reactorbottom or walls, where such segregated heavy molecules act as aprecursor for coke formation. Even in supercritical water reactor, theaggregation of heavy molecules can lead to the formation of coke, andcoke can lead to the formation of hot spots.

A supercritical water process that reduces or prevents the formation ofhot spots would be advantageous. A supercritical water process thatreduces the formation of coke and increases operational stability overconventional supercritical water processes would be advantageous.

SUMMARY

The current invention provides a process and apparatus for the upgradingof a hydrocarbon feedstock with supercritical water, wherein theupgrading process specifically excludes the use of a hydrothermalcatalyst or the use of an external supply of hydrogen.

In a first aspect of the present invention, a process for reducing cokeformation during hydrocarbon upgrading reactions using a double-wallreactor is provided. The process includes the steps of feeding a heatedfeed water to a shell-side volume of the double-wall reactor to producea heat transfer stream. The double-wall reactor includes an exteriorwall and an interior wall, the exterior wall and the interior walldefining the shell-side volume disposed between, a reaction sectionvolume bounded by the interior wall, a heating element, the heatingelement adjacent to the exterior wall, wherein the heating element isconfigured to heat the heat transfer stream to create a hot waterreturn, such that the heat transfer stream is above the criticaltemperature of water, wherein heat is transferred from the heat transferstream through the interior wall to the reaction section volume, whereinthe hot water return exits the shell-side volume, wherein the heattransfer stream is at a temperature greater than the criticaltemperature of water and is at a pressure greater than the criticalpressure of water. The process further includes the steps of feeding thehot water return exiting the shell-side volume of the double-wallreactor through a filter, the filter is configured to removeparticulates to form a filtered water stream, mixing the filtered waterstream with a heated hydrocarbon feedstock in a mixer to produce a mixedstream, wherein the heated hydrocarbon feedstock is at a pressuregreater than the critical pressure of water and at a temperature greaterthan 50° C., feeding the mixed stream to the reaction section volume ofthe double-wall reactor in a flow configuration counter-current to theheat transfer stream to create a reaction flow stream, reacting thereaction flow stream at a reaction temperature in the reaction sectionvolume to produce a reactor effluent, wherein the heat transferred tothe reaction section volume from the heat transfer stream is operable tomaintain the reaction temperature above the critical temperature ofwater, cooling the reactor effluent in a reactor cooler to produce acooled effluent, de-pressurizing the cooled effluent in a pressurereducer to produce a depressurized effluent, separating thedepressurized effluent in a phase separator to produce a gas phaseproduct and a liquid phase product, and separating the liquid phaseproduct in a product separator to produce a separated water stream andan upgraded hydrocarbon stream.

In certain aspects of the present invention, the process furtherincludes the step of recycling the separated water stream to combinewith a feed water upstream of the double-wall reactor. In certainaspects of the present invention, the double-wall reactor furtherincludes a shell-side inlet, the shell-side inlet configured to receivethe heated feed water, a shell-side outlet, the shell-side outletconfigured to eject the heat transfer stream as the hot water return, areaction inlet, the reaction inlet configured to receive the mixedstream, and a reaction outlet, the reaction outlet configured to ejectthe reaction flow stream as the reactor effluent, wherein the shell-sideinlet, the shell-side outlet, the reaction inlet, and the reactionoutlet are configured to create the flow configuration counter-currentbetween the heat transfer stream and the reaction flow stream. Incertain aspects of the present invention, the double-wall reactorfurther includes baffles extending from the exterior wall into theshell-side volume, the baffles configured to increase heat transfer fromthe heating element and the exterior wall to the heat transfer stream.In certain aspects of the present invention, the process furtherincludes the step of feeding the hot water return to a mixer pre-heater,the mixer pre-heater configured to increase the temperature of the hotwater return to produce a hot mixer feed, and feeding the hot mixer feedto the filter to produce the filtered water stream. In certain aspectsof the present invention, the process further includes the step offeeding the heated feed water to a water super heater, the water superheater configured to increase the temperature of the heated feed waterto produce a hot water supply, and feeding the hot water supply to theshell-side volume of the double-wall reactor. In certain aspects of thepresent invention, the process further includes the steps of feeding thereactor effluent to a supercritical water reactor, the supercriticalwater reactor configured to upgrade hydrocarbons present in the reactoreffluent, wherein the temperature of the supercritical water reactor isgreater than the critical temperature of water, wherein the pressure ofthe supercritical water reactor is greater than the critical pressure ofwater, reacting the reactor effluent to produce a product stream, andfeeding the product stream to the reactor cooler. In certain aspects ofthe present invention, liquid yield is greater than 98% by volume. Incertain aspects of the present invention, the upgraded hydrocarbonstream has reduced amounts of asphaltene, sulfur, and other impurities.In certain aspects of the present invention, a residence time of thereaction flow stream in the double-wall reactor is greater than 10seconds.

In a second aspect of the present invention, a supercritical water plantto upgrade hydrocarbons with reduced coke formation is provided. Thesupercritical water plant includes a hydrocarbon feedstock pump, thehydrocarbon feedstock pump configured to pressurize a hydrocarbonfeedstock to a pressure above the critical pressure of water to producea pressurized hydrocarbon feedstock, a hydrocarbon feedstock heaterfluidly connected to the hydrocarbon feedstock pump, the hydrocarbonfeedstock heater configured to heat the pressurized hydrocarbonfeedstock to a temperature greater than 50° C. to produce a heatedhydrocarbon feedstock, a feed water pump, the feed water pump configuredto pressurize a feed water to a pressure above the critical pressure ofwater to produce a pressurized feed water, a feed water heater fluidlyconnected to the feed water pump, the feed water pump configured to heatthe pressurized feed water to a temperature above the criticaltemperature of water to produce a heated feed water, a double-wallreactor, the double-wall reactor configured to upgrade the hydrocarbonswith upgrading reactions, the double-wall reactor further configured tolimit coke formation during the upgrading reactions. The double-wallreactor includes a shell-side inlet fluidly connected to the feed waterheater, the shell-side inlet configured to receive the heated feed waterto produce a heat transfer stream in a shell-side volume, an exteriorwall and an interior wall, the exterior wall and the interior walldefining the shell-side volume disposed between, the shell-side volumeconfigured to receive the heat transfer stream, a reaction sectionvolume bounded by the interior wall, a shell-side outlet fluidlyconnected to the shell-side volume, the shell-side outlet configured toeject the heat transfer stream to produce a hot water return, and aheating element, the heating element adjacent to the exterior wall,wherein the heating element is configured to heat the heat transferstream, such that the heat transfer stream is above the criticaltemperature of water, wherein heat is transferred from the heat transferstream through the interior wall to the reaction section volume. Thesupercritical water plant further includes a filter fluidly connected tothe shell-side outlet, the filter configured to remove particulates fromthe hot water return to form a filtered water stream, a mixer fluidlyconnected to the filter, the mixer configured to mix the filtered waterstream and the heated hydrocarbon feedstock to produce a mixed stream,wherein the mixed stream is supplied to the reaction section volume ofthe double-wall reactor in a flow configuration counter-current to theheat transfer stream to produce a reaction flow stream, wherein thereaction section volume is operable to upgrade the hydrocarbons in thereaction flow stream to produce a reactor effluent, a reactor coolerfluidly connected to the double-wall reactor, the reactor coolerconfigured to cool the reactor effluent to a temperature below thecritical temperature of water to produce a cooled effluent, a pressurereducer fluidly connected to the reactor cooler, the pressure reducerconfigured to reduce the pressure of the cooled effluent to a pressurebelow the critical pressure of water to produce a depressurizedeffluent, a phase separator fluidly connected to the pressure reducer,the phase separator configured to separate the depressurized effluentinto a gas phase product and a liquid phase product, and a productseparator fluidly connected to the phase separator, the productseparator configured to separate the liquid phase product into anupgraded hydrocarbon stream and a separated water stream.

In certain aspects of the present invention, the separated water streamis combined with the feed water upstream of the feed water pump. Incertain aspects of the present invention, the double-wall reactorfurther includes a reaction inlet, the reaction inlet configured toreceive the mixed stream, and a reaction outlet, the reaction outletconfigured to eject the reaction flow stream as the reactor effluent,wherein the shell-side inlet, the shell-side outlet, the reaction inlet,and the reaction outlet are configured to create the flow configurationcounter-current between the heat transfer stream and the reaction flowstream. In certain aspects of the present invention, the double-wallreactor further includes baffles extending from the exterior wall intothe shell-side volume, the baffles configured to increase heat transferfrom the heating element and the exterior wall to the heat transferstream. In certain aspects of the present invention, the supercriticalwater plant further includes a mixer pre-heater fluidly connected to thedouble-wall reactor, the mixer pre-heater configured to increase thetemperature of the hot water return to produce a hot mixer feed, whereinthe hot mixer feed is supplied to the filter to produce the filteredwater stream. In certain aspects of the present invention, thesupercritical water plant further includes a water super heater fluidlyconnected to the feed water heater, the water super heater configured toincrease the temperature of the heated feed water to produce a hot watersupply, wherein the hot water supply is supplied to the shell-sidevolume of the double-wall reactor. In certain aspects of the presentinvention, the supercritical water plant further includes asupercritical water reactor fluidly connected to the double-wallreactor, the supercritical water reactor configured to upgrade unreactedhydrocarbons present in the reactor effluent to produce a productstream, wherein the temperature of the supercritical water reactor isgreater than the critical temperature of water, wherein the pressure ofthe supercritical water reactor is greater than the critical pressure ofwater, wherein the product stream is supplied to the reactor cooler. Incertain aspects of the present invention, liquid yield is greater than98% by volume. In certain aspects of the present invention, the upgradedhydrocarbon stream has reduced amounts of asphaltene, sulfur, and otherimpurities. In certain aspects of the present invention, a residencetime of the reaction flow stream in the double-wall reactor is greaterthan 10 seconds.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescriptions, claims, and accompanying drawings. It is to be noted,however, that the drawings illustrate only several embodiments of theinvention and are therefore not to be considered limiting of theinvention's scope as it can admit to other equally effectiveembodiments.

FIG. 1 provides a process diagram of one embodiment of the method ofupgrading a hydrocarbon feedstock according to the present invention.

FIG. 2 provides a plan view of an embodiment of a double-wall reactor.

FIG. 2a provides a plan view of an embodiment of a double-wall reactor.

FIG. 3 provides a process diagram of one embodiment of the method ofupgrading a hydrocarbon feedstock according to the present invention.

FIG. 4 provides a process diagram of one embodiment of the method ofupgrading a hydrocarbon feedstock according to the present invention.

FIG. 5 provides a process diagram of one embodiment of the method ofupgrading a hydrocarbon feedstock according to the present invention.

FIG. 6 provides a process diagram of one embodiment of the method ofupgrading a hydrocarbon feedstock according to the present invention.

DETAILED DESCRIPTION

Although the following detailed description contains many specificdetails for purposes of illustration, it is understood that one ofordinary skill in the art will appreciate that many examples, variationsand alterations to the following details are within the scope and spiritof the invention. Accordingly, the exemplary embodiments of theinvention described herein and provided in the appended figures are setforth without any loss of generality, and without imposing limitations,relating to the claimed invention. Features of the embodiments can becombined with features of other embodiments.

Referring to FIG. 1, an embodiment of a process for reducing cokeformation in a double-wall reactor is provided. Hydrocarbon feedstock 10is pressurized in hydrocarbon feedstock pump 104 to create pressurizedhydrocarbon feedstock 12. Hydrocarbon feedstock 10 can be from anyhydrocarbon source. Exemplary hydrocarbon sources for use as hydrocarbonfeedstock 10 include whole range crude oil, distilled crude oil, residueoil, vacuum residue oil, topped crude oil, bottom fraction of crude oil,product streams from oil refineries, vacuum gas oil, product streamsfrom steam cracking processes, liquefied coals, liquid productsrecovered from oil or tar sands, bitumen, oil shale, asphaltene, biomasshydrocarbons, and the like. The pressure of pressurized hydrocarbonfeedstock 12 is greater than about 22.064 MPa and alternately betweenabout 22.1 MPa and about 31.9 MPa. In at least one embodiment of thepresent invention, the pressure of pressurized hydrocarbon feedstock 12is 25.0 MPa. The critical pressure of water is 22.064 MPa.

Pressurized hydrocarbon feedstock 12 is heated in hydrocarbon feedstockheater 106 to form heated hydrocarbon feedstock 14. The temperature ofheated hydrocarbon feedstock 14 is between about 10° C. and about 300°C., alternately between about 50° C. and 250° C., alternately betweenabout 50° C. and 200° C., alternately between about 50° C. and 150° C.,alternately between about 50° C. and about 100° C., alternately betweenabout 100° C. and about 200° C., alternately between about 150° C. andabout 250° C., alternately between about 200° C. and about 300° C. In atleast one embodiment of the present invention, the temperature of heatedhydrocarbon feedstock 14 is greater than 50° C. In at least oneembodiment of the present invention, the temperature of heatedhydrocarbon feedstock 14 is 125° C. Hydrocarbon feedstock heater 106 canbe any heat transfer unit capable of heating pressurized hydrocarbonfeedstock 12. Exemplary heat transfer units that can be employed ashydrocarbon feedstock heater 106 include natural gas fired heater, heatexchanger, and electric heater. In some embodiments, pressurizedhydrocarbon feedstock 12 is heated in a cross-exchange operation in aheat exchanger with another process stream. In at least one embodimentof the present invention, hydrocarbon feedstock heater 106 is designedto minimize pressure drop such that the pressure of heated hydrocarbonfeedstock 14 exiting hydrocarbon feedstock heater 106 is above thecritical pressure of water. Heated hydrocarbon feedstock 14 is fed tomixer 108.

Feed water 20 can be any source of water. In at least one embodiment,feed water 20 has a conductivity less than about 10.0 μmhos/cm.Conductivity is the most common way to determine the concentration ofionic compounds in the water. A higher conductivity indicates anincreased presence of ionic compounds in the water. Ionic compounds suchas sodium chloride can precipitate under supercritical water conditions,even though dissolved in water at subcritical conditions. Exemplarysources of water that can be utilized as feed water 20 includedemineralized water, distillated water, boiler feed water, deionizedwater, and treated, recycled water. In at least one embodiment of thepresent invention, feed water 20 is a demineralized water. In at leastone embodiment of the present invention, feed water 20 is in the absenceof brine. In at least one embodiment of the present invention, feedwater 20 includes water recycled from separated water stream 60. Feedwater 20 is pressurized in feed water pump 100 to produce pressurizedfeed water 22. The pressure of pressurized feed water 22 is greater thanabout 22.064 MPa, alternately between about 22.1 MPa and about 31.9 MPa,alternately between about 22.9 MPa and about 31.1 MPa. In at least oneembodiment of the present invention, the pressure of pressurized feedwater 22 is 25.0 MPa. The critical pressure of water is 22.064 MPa.

Pressurized feed water 22 is heated in feed water heater 102 to createheated feed water 24. The temperature of heated feed water 24 is greaterthan about 374° C., alternately between about 374° C. and about 600° C.,alternately between 400° C. and about 550° C., alternately between about400° C. and about 450° C., alternately between 450° C. and about 500°C., alternately between about 500° C. and about 550° C., alternatelybetween about 550° C. and about 600° C. The maximum temperature of thewater is selected in consideration of the materials of construction ofthe double-wall reactor 110 and the associated piping back to feed waterheater 102. In at least one embodiment of the present invention, thetemperature of heated feed water 24 is 520° C. The critical temperatureof water is 373.946° C. Feed water heater 102 can be any type of heattransfer unit capable of heating pressurized feed water 22. Exemplaryheat transfer units to employ as feed water heater 102 include a naturalgas fired heater, a heat exchanger, an electric heater, or any heater orheat exchanger known in the art. In some embodiments of the presentinvention, pressurized feed water 22 is partially heated in across-exchange operation in a heat exchanger with another process streamof the process. Heated feed water 24 is supercritical water, above thecritical temperature and the critical pressure, or critical point ofwater. Above the critical temperature and pressure, the liquid and gasphase boundary of water disappears, and the fluid has characteristics ofboth liquid and gaseous substances. Supercritical water is able todissolve organic compounds like an organic solvent and has excellentdiffusibility like a gas. Regulation of the temperature and pressureallows for continuous “tuning” of the properties of the supercriticalwater to be more liquid or more gas like. Supercritical water hasreduced density and lower polarity, as compared to liquid-phasesub-critical water, thereby greatly extending the possible range ofchemistry which can be carried out in water. Supercritical water hasvarious unexpected properties as it reaches supercritical boundaries.Supercritical water has very high solubility toward organic compoundsand has an infinite miscibility with gases. In certain embodiments,supercritical water generates hydrogen gas through a steam reformingreaction and water-gas shift reaction, which is then available for theupgrading reactions.

Heated feed water 24 is fed to double-wall reactor 110. In at least oneembodiment of the present invention, double-wall reactor 110 sharesfeatures with a double pipe heat exchanger. In at least one embodimentof the present invention, double-wall reactor 110 is designed tospecification based on the process conditions, including flow rate.Double-wall reactor 110 is described with reference to FIG. 2.Double-wall reactor 110 has exterior wall 210 and interior wall 212. Inat least one embodiment of the present invention, exterior wall 210 andinterior wall 212 are formed of two concentric cylinders, open at bothends, the two concentric cylinders are not connected. In at least oneembodiment of the present invention, double-wall reactor 110 is adouble-pipe type vessel with an external heating source. The volumeenclosed by interior wall 212 defines reaction section volume 214. Thevolume between interior wall 212 and exterior wall 210 definesshell-side volume 216. Reaction section volume 214 has one reactioninlet 230 and one reaction outlet 232. Shell-side volume 216 hasshell-side inlet 220 and shell-side outlet 222. Heated feed water 24enters shell-side volume 216 of double-wall reactor 110 throughshell-side inlet 220 to create heat transfer stream 30.

The design of double-wall reactor 110 that restricts exchange of fluidsdirectly between shell-side volume 216 and reaction section volume 214reduces the risk of mechanical failure (at joints, nozzles, ports,etc.), simplifies fabrication of double-wall reactor 110, and providesfor more manageable control of pressure and temperature. Temperaturecontrol in reaction section volume 214 and along interior wall 212 is anadvantage of the present invention.

Heating element 218 is adjacent to exterior wall 210. Heating element218 is any direct heating source. Exemplary direct heating sources foruse as heating element 218 include an electric heater, a gas firedheater, a liquid fired heater, and a coal fired heater. Heating element218 transfers heat to heat transfer stream 30. In at least oneembodiment of the present invention, heating element 218 maintains thetemperature of heat transfer stream 30 relative to the temperature ofheated feed water 24. In at least one embodiment of the presentinvention, heating element 218 extends the entire length orsubstantially the entire length of exterior wall 210. In at least oneembodiment of the present invention, heating element 218 extends forless than the entire length of exterior wall 210. In at least oneembodiment of the present invention, heating element 218 wraps aroundthe entire circumference of exterior wall 210. In at least oneembodiment of the present invention, heating element 218 is adjacent toa portion of the circumference of exterior wall 210. In at least oneembodiment of the present invention, heating element 218 increases thetemperature of heat transfer stream 30 above the temperature of heatedfeed water 24. Heating of heat transfer stream 30 is in the absence ofan oxidation reaction, which can contribute to run-away reactiontemperatures. Heat is transferred from exterior wall 210 through heattransfer stream 30 in shell-side volume 216 to interior wall 212,through interior wall 212 to reaction section volume 214. The volumebetween interior wall 212 and exterior wall 210, the flow rate of heattransfer stream 30, and the temperature of heat transfer stream 30 areoptimized in consideration of heat transfer requirements from exteriorwall 210 through shell-side volume 216 to interior wall 212 and toimprove the efficiency of heat transfer stream 30 as the heat transfermedium. The velocity of heat transfer stream 30 is influenced by thetarget reaction temperature.

In at least one embodiment of the present invention, the efficiency ofheat transfer to heat transfer stream 30 can be improved by installingbaffles 240 adjacent to exterior wall 210 and extending into shell-sidevolume 216. Baffles 240 increase the heat transfer ability of heatingelement 218 to heat transfer stream 30 by increasing the surface areaexposed to the flow of heat transfer stream 30, creating a largersurface that interacts with heat transfer stream 30. Improved heating ofheat transfer stream 30 improves the efficiency of heat transfer fromheat transfer stream 30 to reaction section volume 214. In at least oneembodiment of the present invention, baffles 240 are fins.

Double-wall reactor 110 is designed in consideration of optimizing thereactor parameters. Reactor parameters include residence time, reactororientation, flow direction, reaction volume, reactor aspect ratio, andoperating conditions. Residence time in double-wall reactor 110 is atleast 5 seconds, alternately at least 10 seconds, alternately at least15 seconds, alternately at least 20 seconds, alternately at least 30seconds, and alternately at least 40 seconds. In at least one embodimentof the present invention, the residence time in double-wall reactor 110is at least 10 seconds. Reactor orientation, as used herein, refers tohow the reactor is aligned relative to ground. Exemplary reactororientations include vertical and horizontal. In at least one embodimentof the present invention, double-wall reactor 110 has a vertical reactororientation. Flow direction refers to whether the flow of mixed stream40 is upflow or downflow in a vertical reactor orientation. In an upflowflow direction, reaction inlet 230 of double-wall reactor 110 ispositioned nearer to grade relative to double-wall reactor 110 outletand mixed stream 40 is fed to reaction inlet 230. In a downflow flowdirection, reaction inlet 230 is positioned farther from grade relativeto reaction outlet 232. Reaction volume refers to the total volume ofreaction section volume 214. The reaction volume is calculated inconsideration of desired residence time, heat transfer efficiency ofheated feed water 24, and the reactor aspect ratio. Reactor aspect ratiois the ratio of the length to the diameter of double-wall reactor 110.The aspect ratio plays a role in heat transfer capability, the residencetime, and the flow regime. The operating conditions include reactortemperature and reactor pressure. Reactor temperature is defined as thetemperature of the fluid at the end of reaction section volume 214.

Referring again to FIG. 1, heat transfer stream 30 exits shell-sidevolume 216 of double-wall reactor 110 as hot water return 32. Thetemperature of hot water return 32 is within 10 degrees of thetemperature of heated feed water 24, alternately within 20 degrees,alternately within 30 degrees, alternately within 40 degrees, andalternately within 50 degrees. In at least one embodiment of the presentinvention, the temperature of hot water return 32 is above thetemperature of heated feed water 24. In at least one embodiment of thepresent invention, the temperature of hot water return 32 is below thetemperature of heated feed water 24. Hot water return 32 becomes one ofthe reactants in reaction section volume 214.

Hot water return 32 flows through filter 124 to produce filtered waterstream 36. Filter 124 can be any type of filtering element known in theart that can remove particulates, including char. In at least oneembodiment of the present invention, filter 124 has a metal housing. Inat least one embodiment of the present invention, filter 124 includes aplurality of filtering elements arranged in a parallel assembly.Filtered water stream 36 is fed to mixer 108 to produce mixed stream 40.In at least one embodiment of the present invention, hot water return 32is in the absence of filter 124 and hot water return 32 mixes directlywith heated hydrocarbon feedstock 14 in mixer 108.

Filtered water stream 36 and heated hydrocarbon feedstock 14 are mixedexternally from double-wall reactor 110. Double-wall reactor 110 is inthe absence of features designed to enhance mixing of reactants. Mixingheated hydrocarbon feedstock 14 and filtered water stream 36 indouble-wall reactor 110 reduces the ability to maintain control oftemperature, pressure, and flow-rate in double-wall reactor 110 creatingunstable conditions in double-wall reactor 110. Mixing heatedhydrocarbon feedstock 14 and filtered water stream 36 upstream ofdouble-wall reactor 110 (externally to double-wall reactor 110) ensuresa more uniform temperature profile of mixed stream 40 when enteringdouble-wall reactor 110 and as it moves through reaction section volume214 as reaction flow stream 42, as shown in FIG. 2. Mixer 108 can be anytype of mixing device capable of mixing filtered water stream 36 andheated hydrocarbon feedstock 14. In at least one embodiment of thepresent invention, mixer 108 is an inline mixer. Mixed stream 40 has aratio of water to hydrocarbons represented by a ratio of the volumetricflow rate of feed water 20 (υ20) to the volumetric flow rate ofhydrocarbon feedstock 10 (υ10). The ratio of υ20 to υ10 is in the rangefrom about 10:1 to about 1:10 as measured at standard ambienttemperature and pressure, alternately about 5:1 to about 1:5 as measuredat standard ambient temperature and pressure, alternately less than 4:1as measured at standard ambient temperature and pressure, alternatelyless than 3:1 as measured at standard ambient temperature and pressure,and alternately less than 2:1 as measured at standard ambienttemperature and pressure. In at least one embodiment of the presentinvention, the ratio of υ20 to υ10 is 1.4:1 as measured at standardambient temperature and pressure. In at least one embodiment of thepresent invention, the ratio of υ20 to υ10 is 2.5:1 as measured atstandard ambient temperature and pressure. Mixed stream 40 is fed toreaction section volume 214 of double-wall reactor 110. As used herein,“standard ambient temperature and pressure” refers to 25° C. and 0.1MPa. Standard temperature and pressure refers to 0° C. and 0.1 MPa.Standard ambient temperature and pressure is more applicable.

Mixed stream 40 and heated feed water 24 are fed to double-wall reactor110 in a counter-current flow configuration as illustrated in FIG. 2. Acounter-current flow configuration as used herein refers to the flowdirection of the streams and means that the streams in double-wallreactor 110 enter the vessel from opposite ends, such that the feedlocation of one stream is adjacent to the exit location of a secondstream. The counter-current flow configuration maintains uniform orsubstantially uniform temperature distribution in reaction flow stream42 throughout the length of reaction section volume 214. Reaction flowstream 42 receives heat through interior wall 212 via indirect heatingfrom heat transfer stream 30 to maintain reaction flow stream 42 at thereaction temperature. Reaction flow stream 42 is continuous flow. Heattransfer stream 30 is continuous flow.

Double-wall reactor 110 is a supercritical reactor. Double-wall reactor110 employs supercritical water as the reaction medium in reactionsection volume 214 for hydrocarbon upgrading reactions in the absence ofexternally-provided hydrogen gas. Double-wall reactor 110 is in theabsence of externally-provided oxidant. In at least one embodiment ofthe present invention, double-wall reactor 110 is in the absence of acatalyst. In at least one embodiment of the present invention,supercritical water acts as a diluent in double-wall reactor 110. Thestructure of double-wall reactor 110 reduces the formation of coke byproviding indirect heating to reaction section volume 214. The absenceof direct heating on interior wall 212 generates a uniform temperaturedistribution on interior wall 212. The uniform temperature distributionreduces or eliminates the formation of hot spots on interior wall 212.The reduction of hot spots reduces the formation of coke inside reactionsection volume 214. Exothermic and endothermic reactions affect theability to control reaction temperature due to localized heating orcooling associated with the exothermic or endothermic reactions,respectively. Without being bound to a particular theory, it is believedthat hydrocarbon fluid reactors that have non-uniform distribution ofcomponents and/or temperatures, also have non-uniform local temperaturedue to the exothermic or endothermic reactions. Double-wall reactor 110,by producing a uniform temperature distribution, therefore reducesexothermic and/or endothermic reactions.

Reaction section volume 214 of double-wall reactor 110 produces reactoreffluent 50. In at least one embodiment of the present invention, thetemperature of reactor effluent 50 is less than the reactor temperaturedue to cooling through the piping at the end of double-wall reactor 110(not shown). In at least one embodiment of the present invention, thetemperature of reactor effluent 50 is greater than the temperature ofmixed stream 40 due to the indirect heating in double-wall reactor 110.The reaction products in reactor effluent 50 are attributable to thecomposition of hydrocarbon feedstock 10, the ratio of υ20 to υ10, andthe operating temperature of reaction section volume 214 of double-wallreactor 110.

Reactor effluent 50 is cooled in reactor cooler 112 to create cooledeffluent 52. Cooled effluent 52 has a temperature between about 10° C.and about 200° C., alternately between about 30° C. and about 120° C.,alternately between about 50° C. and about 100° C. In at least oneembodiment of the present invention, the temperature of cooled effluent52 is 60° C. Reactor cooler 112 can be any heat transfer unit capable ofcooling reactor effluent 50. Exemplary heat transfer units that can beemployed as reactor cooler 112 include heat exchangers, steamgenerators, cross-exchangers, or air coolers. According to at least oneembodiment of the present invention as shown in FIG. 5, reactor cooler140 is a cross-exchanger that heats pressurized feed water 22 with heatfrom reactor effluent 50, and in the process cools reactor effluent 50.One of skill in the art will appreciate that cross-exchange heatexchangers can be utilized to provide energy recovery within the system.

The pressure of cooled effluent 52 is reduced in pressure reducer 114 toform depressurized effluent 54. The pressure of depressurized effluent54 is between about 0.11 MPa and about 2.2 MPa, alternately betweenabout 0.05 MPa and about 1.2 MPa, alternately between about 0.05 MPa andabout 1.0 MPa, alternately between about 0.11 MPa and about 0.5 MPa. Inat least one embodiment of the present invention, the pressure ofdepressurized effluent 54 is 0.11 MPa. In at least one embodiment of thepresent invention, the pressure of depressurized effluent 54 isatmospheric pressure (101.3 kPa). Pressure reducer 114 can be any typeof depressurizing device capable of reducing the pressure of cooledeffluent 52. Exemplary devices suitable for use as pressure reducer 114include pressure control valve and capillary-type pressure let-downdevices. Depressurized effluent 54 is fed to phase separator 116.

Reactor effluent 50, cooled effluent 52, and depressurized effluent 54contain water, upgraded hydrocarbons, and other hydrocarbons.Depressurized effluent 54 further includes gases, such as carbondioxide. Reactor effluent 50, cooled effluent 52, and depressurizedeffluent 54 have a higher content of light hydrocarbons as compared tohydrocarbon feedstock 10. The boiling point range of hydrocarbons indepressurized effluent 54 is lower compared to the boiling point rangeof hydrocarbons present in hydrocarbon feedstock 10. A lower boilingpoint range of hydrocarbons indicates a lower content of heavy fractionhydrocarbons. The mass fraction of water present in reactor effluent 50,cooled effluent 52, and depressurized effluent 54 depends on theoperating conditions in double-wall reactor 110, the flow rate of feedwater 20 and the feed ratio of water to hydrocarbon in mixed stream 40.

Phase separator 116 separates depressurized effluent 54 into gas phaseproduct 56 and liquid phase product 58. Phase separator 116 is agas-liquid separator. Exemplary separators for use as phase separator116 include flash drum, flash column, multi-stage column, stripping-typecolumn.

The operating conditions of reactor cooler 112, pressure reducer 114,and phase separator 116 are adjusted in consideration of the processingsteps performed on gas phase product 56 and liquid phase product 58. Theoperating conditions of reactor cooler 112, pressure reducer 114, andphase separator 116 influence the total amount and the compositions ingas phase product 56 and liquid phase product 58.

Gas phase product 56 can be sent for further processing to recovercomponents in the stream or alternately can be sent for processing anddisposal. In at least one embodiment of the present invention, gas phaseproduct 56 contains light hydrocarbon gases, including methane, ethane,ethylene, propane, and propylene. In at least one embodiment of thepresent invention, gas phase product 56 can be used as fuel gas. In atleast one embodiment of the present invention, gas phase product 56contains light hydrocarbon gases and hydrogen sulfide.

Liquid phase product 58 is fed to product separator 118 to separateliquid phase product 58 into upgraded hydrocarbon stream 62 andseparated water stream 60. Upgraded hydrocarbon stream 62 containsreduced impurities compared to hydrocarbon feedstock 10. Upgradedhydrocarbon stream 62 can be sent for further processing, can be pooledwith other upgraded hydrocarbons, or can be used in any other capacityappropriate for an upgraded hydrocarbon stream. The liquid yield ofupgraded hydrocarbon stream 62 to hydrocarbon feedstock 10 was greaterthan 95%, alternately greater than 98%, alternately greater than 98.5%,and alternately greater than 99%. In at least one embodiment of thepresent invention, the liquid yield was greater than 98%. Liquid yieldis a percentage of the total weight of upgraded hydrocarbon stream 62divided by the total weight of hydrocarbon feedstock 10. Liquid yieldwill be less than 100% because of loss of gases and water, whereinhydrocarbons are dissolved in water. Separated water stream 60 can besent for further processing, can be stored onsite, can be sent fordisposal, or can be recycled to the front of the process. In at leastone embodiment of the present invention, separated water stream 60 isrecycled to be mixed with or to be used as feed water 20. Separatedwater stream 60 contains a total organic carbon content. The totalorganic carbon content is in the form of normal alkanes, aromaticcompounds, and other hydrocarbons. Aromatic hydrocarbons have a highersolubility in supercritical water relative to normal alkanes. Removal ofhydrocarbons from separated water stream 60 that is to recycled to thesupercritical water process in double-wall reactor 110 is important toavoid the production of char due to hydrocarbon decomposition, which canplug the process lines. In at least one embodiment of the presentinvention, separated water stream 60 is treated to achieve a totalorganic carbon content of less than 20,000 ppm by weight, alternatelyless than 10,000 ppm by weight, alternately less than 5,000 ppm byweight, and alternately less than 1,000 by weight.

Process instrumentation and analyzers can be added to the system toimprove the composition of upgraded hydrocarbon stream 62 by improvingheating and pressure control of the process units.

Referring to FIG. 3, an embodiment of the present invention is shown.According to the embodiment of the present invention as shown in FIG. 3and with reference to FIG. 1 described herein, hot water return 32 exitsshell-side volume 216 of double-wall reactor 110 and is fed to mixerpre-heater 120 to produce hot mixer feed 34. Mixer pre-heater 120 can beany type of heat transfer unit capable of heating hot water return 32.Exemplary heat transfer units for use as mixer pre-heater 120 include anatural gas fired heater, a heat exchanger, an electric heater, or anyheater or heat exchanger known in the art. Hot mixer feed 34 is heatedto a temperature above 374° C., alternately to a temperature above thetemperature of hot water return 32 when it exits shell-side volume 216,and alternately to a temperature between the temperature of hot waterreturn 32 when it exits shell-side volume 216 and 600° C. In at leastone embodiment of the present invention, mixer pre-heater 120 increasesthe temperature of hot water return 32. Hot mixer feed 34 mixes withheated hydrocarbon feedstock 14 in mixer 108 to produce mixed stream 40.

Referring to FIG. 4, an embodiment of the present invention is shown.According to the embodiment of the present invention as shown in FIG. 4and with reference to FIG. 1 described herein, heated feed water 24exits feed water heater 102 and is introduced to water super heater 122to produce hot water supply 26. Water super heater 122 can be any typeof heat transfer unit capable of heating heated feed water 24. Exemplaryheat transfer units for use as water super heater 122 include a naturalgas fired heater, a heat exchanger, an electric heater, or any heater orheat exchanger known in the art. Hot water supply 26 is heated to atemperature above 374° C., alternately to a temperature above thetemperature of heated feed water 24 when it exits feed water heater 102,and alternately to the temperature between the temperature of heatedfeed water 24 when it exits feed water heater 102 and 600° C. In atleast one embodiment of the present invention, water super heater 122,increases the temperature of heated feed water 24. Feed water heater 102and water super heater 122 can be balanced for efficient heating toproduce hot water supply 26. Hot water supply 26 is fed to shell-sidevolume 216 of double-wall reactor 110.

Referring to FIG. 6, an embodiment of the present invention is shown.According to the embodiment of the present invention as shown in FIG. 6and with reference to FIG. 1 described herein, pressurized feed water 22is heated in feed water cross-exchanger 126 by cross exchanging withproduct stream 70. Heating pressurized feed water 22 produces heatedfeed water 24 which is then fed to shell-side volume 216 of double-wallreactor 110 as described with reference to FIG. 1. Reactor effluent 50is fed to supercritical water reactor 130 downstream of double-wallreactor 110.

Supercritical water reactor 130 is a supercritical reactor. Double-wallreactor 110 and supercritical water reactor 130 are in a two-reactor inseries configuration. In a two-reactor in series configuration, thefirst reactor, double-wall reactor 110, ensures mixing of hydrocarbonsand supercritical water and upgrading reactions begin to occur. In thesecond reactor, supercritical water reactor 130, the bulk of upgradingreactions occur, including cracking, desulfurization, and isomerizationreactions. Ensuring the components are well-mixed in the first reactoreliminates all or substantially all of the hot spots in the secondreactor. The elimination of hot spots prevents all or substantially allof the coke from forming in the second reactor. In at least oneembodiment of the present invention, supercritical water reactor 130 isa single-wall reactor with a direct heating source. In at least oneembodiment of the present invention, the second reactor is a double-wallreactor with a reaction section that is heated with indirect heating. Inat least one embodiment of the present invention, the reactor parametersof double-wall reactor 110 and the reactor parameters of supercriticalwater reactor 130 are the same. In at least one embodiment of thepresent invention, the reactor parameters of double-wall reactor 110 andthe reactor parameters of supercritical water reactor 130 are different.In at least one embodiment of the present invention, at least one of thereactor parameters of double-wall reactor 110 is the same assupercritical water reactor 130 and at least one of the reactorparameters of double-wall reactor 110 is different than supercriticalwater reactor 130. Supercritical water reactor 130 produces productstream 70. Product stream 70 is fed to feed water cross-exchanger 126.Product stream 70 is cooled in feed water cross-exchanger 126 to producecooled effluent 52.

EXAMPLE Comparative Example

Two simulations were created to compare a single-wall reactor and thedouble-wall reactor of the present invention. In both simulations, ahydrocarbon feedstock at a rate of 10 barrels/day was pressurized to apressure of 25.0 MPa and heated to a temperature of 125° C.

In the single-wall reactor simulation, the hydrocarbon feedstock wasmixed with a feed water at a pressure of 25.0 MPa and a temperature of460° C. The water stream was a water recycle stream from the liquidseparator downstream of the reactor. The single-wall reactor wassimulated as a tubular vessel having an internal volume of 10 L. Theliquid yield was 95 wt %. Table 1 includes the operating conditions ofthe various streams. Table 2 shows the properties of the hydrocarbonfeedstock and the upgraded hydrocarbon streams.

TABLE 1 Stream Operating Conditions Heated Stream Hydrocarbon WaterHydrocarbon Heated Mixed Reactor Cooled Depressurized Name FeedstockFeed Feedstock Water Stream Effluent Effluent Stream Temp 25 25 125 460365 450 50 45 (° C.) Pressure 0.11 0.11 25.0 25.0 25.0 24.8 24.6 0.11(MPa)

TABLE 2 Stream Properties Hydro- Upgraded carbon Hydrocarbon PropertiesFeedstock Stream Specific Gravity (API) 17 24 Asphaltene (wt %) 13.0 2.0Sulfur (wt % S) 3.2 2.6

In the double-wall reactor simulation, the embodiment was simulated asdescribed with reference to FIG. 1. Feed water 20 was pressurized to apressure of 25.0 MPa and heated to a temperature of 450° C. and then fedto shell-side volume 216 of double-wall reactor 110 as heated feed water24. Hot water return 32 exiting double-wall reactor 110 was mixed withheated hydrocarbon feedstock 14 and fed to reaction section volume 214of double-wall reactor 110 in a counter-current flow configuration toheated feed water 24. Feed water 20 was recycled from product separator118 as at least a fraction of separated water stream 60. The temperatureof hot water return 32 was 480° C. due to heating element 218 onexterior wall 210 of double-wall reactor 110. In the simulation, heatingelement 218 was simulated as an external gas fired heater. Liquid yieldwas 98 wt %. The operating conditions are in Table 3. The streamproperties are in Table 4.

TABLE 3 Stream Operating Conditions Heated Heated Hydrocarbon FeedHydrocarbon Feed Mixed Reactor Cooled Stream Feedstock Water FeedstockWater Stream Effluent Effluent Depressurized Name 10 20 14 24 40 50 52Effluent 54 Temp 25 25 125 450 373 430 50 50 (° C.) Pressure 0.11 0.1125.0 25.0 25.0 25.0 24.8 0.11 (MPa)

TABLE 4 Stream Properties Hydro- Upgraded carbon Hydrocarbon PropertiesFeedstock Stream Specific Gravity (API) 17 25 Asphaltene (wt %) 13.0 1.8Sulfur (wt % S) 3.2 2.5

Without being bound to any particular theory, it is believed that theabsence of hot spots in the double-wall reactor as compared to thesingle-wall reactor resulted in the higher liquid yield, 98 wt % for thedouble-wall reactor vs. 95 wt % for the single-wall reactor, and betterquality product, lower asphaltene weight percent and sulfur weightpercent, even at lower reactor temperature, 430° C. for the double-wallreactor vs. 450° C. for the single-wall reactor. It is suspected thathot spots in the single-wall reactor simulation induced condensationreactions between heavy molecules, which caused coke formation, as wellas over-cracking to produce gas phase product. Condensation reactiontraps sulfur and metals in the heavier molecules that are products ofcondensation reactions.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereupon without departing from the principle and scope of theinvention. Accordingly, the scope of the present invention should bedetermined by the following claims and their appropriate legalequivalents.

The singular forms “a”, “an” and “the” include plural referents, unlessthe context clearly dictates otherwise.

Optional or optionally means that the subsequently described event orcircumstances may or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value and/or to the other particular value, along withall combinations within said range.

That which is claimed is:
 1. A supercritical water plant to upgradehydrocarbons with reduced coke formation, the supercritical water plantcomprising: a hydrocarbon feedstock pump, the hydrocarbon feedstock pumpconfigured to pressurize a hydrocarbon feedstock to a pressure above thecritical pressure of water to produce a pressurized hydrocarbonfeedstock; a hydrocarbon feedstock heater fluidly connected to thehydrocarbon feedstock pump, the hydrocarbon feedstock heater configuredto heat the pressurized hydrocarbon feedstock to a temperature greaterthan 50° C. to produce a heated hydrocarbon feedstock; a feed waterpump, the feed water pump configured to pressurize a feed water to apressure above the critical pressure of water to produce a pressurizedfeed water; a feed water heater fluidly connected to the feed waterpump, the feed water pump configured to heat the pressurized feed waterto a temperature above the critical temperature of water to produce aheated feed water; a double-wall reactor, the double-wall reactorconfigured to upgrade the hydrocarbons with upgrading reactions, thedouble-wall reactor further configured to limit coke formation duringthe upgrading reactions, the double-wall reactor comprising: ashell-side inlet fluidly connected to the feed water heater, theshell-side inlet configured to receive the heated feed water to producea heat transfer stream in a shell-side volume; an exterior wall and aninterior wall, the exterior wall and the interior wall defining theshell-side volume disposed between, the shell-side volume configured toreceive the heat transfer stream; a reaction section volume bounded bythe interior wall; a shell-side outlet fluidly connected to theshell-side volume, the shell-side outlet configured to eject the heattransfer stream to produce a hot water return; and a heating element,the heating element adjacent to the exterior wall, wherein the heatingelement is configured to heat the heat transfer stream, such that theheat transfer stream is above the critical temperature of water, whereinheat is transferred from the heat transfer stream through the interiorwall to the reaction section volume; a filter fluidly connected to theshell-side outlet, the filter configured to remove particulates from thehot water return to form a filtered water stream; a mixer fluidlyconnected to the filter, the mixer configured to mix the filtered waterstream and the heated hydrocarbon feedstock to produce a mixed stream,wherein the mixed stream is supplied to the reaction section volume ofthe double-wall reactor in a flow configuration counter-current to theheat transfer stream to produce a reaction flow stream, wherein thereaction section volume is operable to upgrade the hydrocarbons in thereaction flow stream to produce a reactor effluent; a reactor coolerfluidly connected to the double-wall reactor, the reactor coolerconfigured to cool the reactor effluent to a temperature below thecritical temperature of water to produce a cooled effluent; a pressurereducer fluidly connected to the reactor cooler, the pressure reducerconfigured to reduce the pressure of the cooled effluent to a pressurebelow the critical pressure of water to produce a depressurizedeffluent; a phase separator fluidly connected to the pressure reducer,the phase separator configured to separate the depressurized effluentinto a gas phase product and a liquid phase product; and a productseparator fluidly connected to the phase separator, the productseparator configured to separate the liquid phase product into anupgraded hydrocarbon stream and a separated water stream.
 2. Thesupercritical water plant of claim 1, wherein the separated water streamis combined with the feed water upstream of the feed water pump.
 3. Thesupercritical water plant of claim 1, wherein the double-wall reactorfurther comprises: a reaction inlet, the reaction inlet configured toreceive the mixed stream; and a reaction outlet, the reaction outletconfigured to eject the reaction flow stream as the reactor effluent,wherein the shell-side inlet, the shell-side outlet, the reaction inlet,and the reaction outlet are configured to create the flow configurationcounter-current between the heat transfer stream and the reaction flowstream.
 4. The supercritical water plant of claim 1, wherein thedouble-wall reactor further comprises: baffles extending from theexterior wall into the shell-side volume, the baffles configured toincrease heat transfer from the heating element and the exterior wall tothe heat transfer stream.
 5. The supercritical water plant of claim 1,further comprising: a mixer pre-heater fluidly connected to thedouble-wall reactor, the mixer pre-heater configured to increase thetemperature of the hot water return to produce a hot mixer feed, whereinthe hot mixer feed is supplied to the filter to produce the filteredwater stream.
 6. The supercritical water plant of claim 1, furthercomprising: a water super heater fluidly connected to the feed waterheater, the water super heater configured to increase the temperature ofthe heated feed water to produce a hot water supply, wherein the hotwater supply is supplied to the shell-side volume of the double-wallreactor.
 7. The supercritical water plant of claim 1, furthercomprising: a supercritical water reactor fluidly connected to thedouble-wall reactor, the supercritical water reactor configured toupgrade unreacted hydrocarbons present in the reactor effluent toproduce a product stream, wherein the temperature of the supercriticalwater reactor is greater than the critical temperature of water, whereinthe pressure of the supercritical water reactor is greater than thecritical pressure of water, wherein the product stream is supplied tothe reactor cooler.
 8. The supercritical water plant of claim 1, whereina liquid yield of the upgraded hydrocarbon is greater than 98% byvolume.
 9. The supercritical water plant of claim 1, wherein theupgraded hydrocarbon stream has reduced amounts of asphaltene, sulfur,and other impurities relative to the hydrocarbon feedstock.
 10. Thesupercritical water plant of claim 1, wherein a residence time of thereaction flow stream in the double-wall reactor is greater than 10seconds.